The present application relates to a recording apparatus that uses an MOPA (Master Oscillator Power Amplifier) in which a mode-lock oscillation type laser and an optical amplifier are combined as a recording optical source.
High-peak power laser light, particularly, ultra-short pulse light, is very effective for realizing the procedure of nonlinear multi-photon absorption.
This procedure of the nonlinear multi-photon absorption is expected to be applied to three-dimensional optical recording, ultra-fine processing, non-destructive bio-imaging, or the like.
For example, there has been reported a method of realizing multi-layer recording by emitting high-power laser light to a transparent bulk material having a nonlinear effect (see ISOM2009 Digest Th-1-01, 2009 by Seiji Kobayashi, Kimihiro Saito, Takashi Iwamura, Hisayuki Yamatsu, Toshihiro Horigome, Mitsuaki Oyamada, Kunihiko Hayashi, Daisuke Ueda, Norihiro Tanabe and Hirotaka Miyamoto).
According to this method, recording on a large-capacity recording medium can be realized more cheaply than a lamination type disc according to the related art.
A mode-lock type titanium-sapphire laser has been used as an optical source that outputs high-power laser light. Even in the example of ISOM2009 Digest Th-1-01, 2009 by Seiji Kobayashi, Kimihiro Saito, Takashi Iwamura, Hisayuki Yamatsu, Toshihiro Horigome, Mitsuaki Oyamada, Kunihiko Hayashi, Daisuke Ueda, Norihiro Tanabe and Hirotaka Miyamoto, emission light of a titanium-sapphire laser with 810 nm is converted into light with a 405 nm wavelength by an SHG (Second Harmonic Generator) and is used in a short-wavelength recording optical source advantageous for high-density recording.
Such a large expensive solid-state laser is limited to applications to experiments in laboratories (for example, see Spectra-Physics Inc. Online (searched in Aug. 6, 2010), Internet i_Series_Data_Sheet.pdf>).
For this reason, many researchers have tried to develop a small-sized and stable pulse optical source as a semiconductor base to put to practical use.
In the next-generation optical recording, as in the above-mentioned method, a blue-purple laser optical source advantageous for the high-density recording of all semiconductors is strongly preferred.
For example, in a gain switching type laser, it has been reported that when strongly excited driving is repeatedly performed at 1 MHz, the peak power of 55 W has been realized (see Appl. Phys. Lett. 96, 051102, 2010 by M. Kuramoto, T. Oki, T. Sugahara, S. Kono, M. Ikeda, and H. Yokoyama).
However, a higher repetition frequency is necessary even in a data recording optical source according to a request for a high data transmission rate in the market.
In recent years, it has been reported that an optical source of 100 W has been realized at a repetition frequency of 1 GHz by a blue laser effective for high-density recording (for example, see APPLIED PHYSICS LETTERS 97, 021101, 2010 by Rintaro Koda, Tomoyuki Oki, Takao Miyajima, Hideki Watanabe, Masaru Kuramoto, Masao Ikeda, and Hiroyuki Yokoyama).
This optical source has a configuration called an MOPA (Master Oscillator Power Amplifier) in which a semiconductor mode-lock laser and a semiconductor optical amplifier are combined.
A recording reproduction apparatus has to record data used in recording at an arbitrarily position based on a wobble signal read from an optical recording medium.
At this time, it is necessary to modulate the recording data in synchronization with an oscillation pulse.